Causes and Countermeasures of side wall transverse cracking of 304 stainless steel products

May 3, 2022

In the process of deep drawing, stainless steel products often appear various kinds of cracking phenomenon, in which the lateral or point cracking of side wall is the common failure form of 304 stainless steel products such as heat preservation cup and pressure cooker. Especially in recent years, with the continuous promotion of cost reduction in product processing, for example, the number of drawing passes of thermos cup has been reduced from 5 to 3, and the annealing process has been changed from multiple annealing in the middle to one or no annealing after stamping. Therefore, higher requirements have been put forward for the formability of stainless steel. The lateral or point cracks on the side wall of stainless steel products may be caused by the inclusion of materials δ The intergranular defects of ferrite and other materials may also be caused by the drawing process and drawing oil in the processing of stainless steel products.

The transverse or punctate cracking of 304 stainless steel insulation cup is mainly caused by inclusions or cracks in the material matrix δ Therefore, the following two points should be well controlled in the production process of stainless steel

(1) Improve the purity of the material and reduce the content of inclusions in the stainless steel matrix.

(2) Improve the composition design and hot and cold rolling annealing process to reduce the content of carbon in stainless steel matrix δ The content of ferrite.

However, these two kinds of manufacturing defects will inevitably exist in the production process of stainless steel materials, so appropriate process measures can be taken to reduce or avoid inclusions or defects in the processing of products such as thermos cups δ The cracks caused by ferrite defects are as follows

(1) The forming method is changed from thinning drawing to equal thickness drawing.

(2) Increase the drawing pass, increase the radius of die fillet, reduce the difficulty of material deformation.

(3) Increase the viscosity of the drawing oil appropriately to promote the uniform deformation of the material and avoid excessive stress concentration.